Rudeness almost upset consumer (3,4)
I believe the answer is:
end user
'consumer' is the definition.
(I know that end-user is a type of consumer)
'rudeness almost upset' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'upset' indicates anagramming the letters.
'rudeness' with its last letter taken away is 'rudenes'.
'rudenes' anagrammed gives 'END-USER'.
(Other definitions for end user that I've seen before include "Recipient of product sold" , "Person for whom a product is destined" , "One who finally receives a product" , "Ensured (anag.)" , "Customer" .)